Method of manufacturing a modular magnetic head assembly

ABSTRACT

A nonmagnetic holder is made having a plurality of precisely located parallel grooves. Each groove has a reference lateral surface provided therein. Individual magnetic transducers are inserted in each groove with a lateral surface abutting the reference lateral surface within that groove. The transducers are preferably made by well known batch fabrication techiques. A locating element, such as a leaf spring, is provided in each groove to urge the transducer core against the reference surface and to firmly hold the transducer in a desired position during alignment and assembly. The modular structure allows inspecting the individual transducers for mechanical or electrical damages and their replacement, if necessary, prior to the final assembly. The multichannel head is then integrally joined together, for example by bonding. The rejection rate of the resulting modular multichannel head is significantly reduced.

The Government has rights in this invention pursuant to Contract No.F33657-81-C-1030 awarded by the U.S. Government.

This is a division of co-pending application Ser. No. 680,873 filed onDec. 12, 1984.

The invention relates to a multichannel magnetic head assembly having amodular structure and to a method of manufacturing the assembly. Inparticular, the invention relates to a modular multichannel headassembly having a simplified structure and made by a simplifiedmanufacturing process. The multichannel head of the invention has highlyaccurate transducing channel locations and it is suitable for recordingon, or reproducing information signals from, narrow tracks of a magneticmedium. Two or more heads may be utilized to obtain interlaced parallelchannels for high density narrow track recording/reproduction.

Multichannel magnetic heads are known to have a plurality of paralleltransducing channels for recording information signals on a moveablerecording medium or for reproducing previously recorded signals from amedium. Each transducing channel has a magnetic core with twocorresponding poles forming a transducing gap between them and atransducing winding wound around the core.

One type of conventional multichannel head employs two correspondingholders, made of a nonmagnetic material and commonly referred to as sidepieces. Each side piece has a plurality of parallel grooves providedtherein. The grooves of both side pieces must be in perfect alignmentwith each-other. Each groove receives a portion of the magnetic core,also referred to as a core member or core piece. Each core memberdefines a magnetic pole and it is firmly attached to the holder. Anon-magnetic transducing gap forming material is provided on the poles.When the corresponding side pieces carrying the core portions areassembled together, the corresponding core portions forming eachtransducer must be accurately aligned to define uniform transducing gapson each channel. During the assembly the side pieces are broughttogether under mechanical pressure to force the corresponding coreportions together. While under pressure, the thusly assembledmultichannel head is bonded together, to obtain an integral multichannelhead structure.

During the final assembly and bonding of these conventional multichannelheads the magnetic core pieces are submitted to stress. Consequently,these core pieces frequently chip, crack or break. Particularly, corepieces made of hard, brittle magnetic material, such as ferrite, havinga small width, for example in the order of several thousands of an inch,are particularly susceptible to mechanical damage. If one or morechannels of the multichannel head are found to be defective, the entirehead assembly must be rejected.

For high performance multichannel heads it is essential to obtain anaccurate channel-to-channel spacing, generally referred to as trackpitch, as well as uniform recording track width on all channels to allowsignals recorded with a particular head to be reproduced with adifferent head. To obtain precise registration between the correspondingcore pieces of each head half, manufacturing of these known multichannelhead structures included the use of a gauge mechanism which served toaccurately position the core pieces of the head halves in mirrorsymmetry. However, manufacturing of the precision gauges is relativelyexpensive. Also, the method of manufacturing the multichannel headutilizing such gauges is labor intensive and therefore expensive.

SUMMARY OF THE INVENTION

The above-indicated disadvantages of known multichannel magnetic headsare significantly reduced by the modular multichannel structure andmethod of the invention.

In accordance with the present invention a holder of nonmagneticmaterial receives a plurality of individual magnetic transducers. Thetransducers are arranged in parallel grooves within the holder. Eachgroove has a reference lateral surface provided therein to support alateral surface of the transducer inserted in the groove. A locatingelement within each groove urges the transducer core against the lateralsurface to obtain an accurate channel-to-channel spacing determined bythe spacing of the lateral surfaces. When all the transducers are inplace, they are integrally joined with the holder to obtain a desiredrigid multichannel transducer structure.

It follows from the foregoing description that the modular structure ofthe multichannel head of the invention allows replacing defective orimperfect individual transducers prior to the final joining of theassembly together. The rejection rate of the resulting multichannelheads is thereby significantly reduced.

Another significant advantage is that track pitch tolerances areminimized by providing a reference lateral surface directly within eachgroove and by referencing the location of each transducer to thatreference surface.

A further important advantage is eliminating the use of precision gaugesfor accurately locating the transducer cores within the grooves of theholder.

There is a further significant advantage of the present invention inthat the individual transducers arranged in the respective transducingchannels may be made by conventional batch fabrication techniques. Forexample, commercially available transducers such as are well known to beused for television signal recording or reproduction can be utilized.The foregoing significantly reduces the cost of manufacturing themultichannel head of the invention.

The foregoing and further features and advantages of the invention willbe better understood from the following description with reference tothe accompanying drawings illustrating preferred and alternativeembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are perspective views showing opposite sides of a priorart transducer.

FIG. 2 is a an exploded perspective view of a nonmagnetic transducercore holder, and of a transducer and leaf spring located therein, inaccordance with the preferred embodiment of the invention.

FIGS. 3A to 3C are respective top, side and front elevation views of amultichannel transducer assembly in accordance with the preferredembodiment of the invention.

FIG. 4A is an exploded perspective view of an alternative embodiment ofthe invention;

FIG. 4B is a perspective view of a portion of an assembled multichannelhead of FIG. 4A; and

FIG. 5 is a schematic top view of a plurality of multichannel transducerassemblies of the invention for obtaining interlaced transducingchannels.

DETAILED DESCRIPTION

FIGS. 1A and 1B show an example of a well known magnetic transducer 20.It will be understood from the description below that the particulartransducer 20 of in FIGS. 1A and 1B represents only one example of atransducer which may be utilized in the multichannel head in accordancewith the preferred embodiment of the present invention. Alternatively,other well known transducers may be utilized.

One such prior art transducer is described for example in U.S. Pat. Nos.3,813,693 and 3,845,550 to Beverley R. Gooch, which patents are commonlyowned by Ampex Corporation, the assignee of this patent application.

With reference to FIGS. 1A and 1B, each shows a perspective view of anopposite side 18 and 19 of a conventional transducer 20. As it is wellknown in the art, the transducer 20 has two corresponding core members21, 22 abutting at a transducing gap plane 32. A nonmagnetic transducergap forming material is provided at respective pole faces 24, 25 todefine a transducing gap 23 therebetween. The width W1 of the abuttingpole faces 24, 25 defines the transducing gap width which preferably issubstantially smaller than the width W2 of the cores 21, 22. Thatreduced width W1 is obtained by providing a notch 26 inwardly of onelateral surface 18 of the transducer 20. The notch 26 is filled with anonmagnetic material, preferably glass. The resulting glass pocket 26 ismade flush with the transducer face 27 and with the lateral surface 18.In the preferred embodiment, the core members 21, 22 are made preferablyof a magnetic ferrite material, for example PS52 manufactured by AmpexCorporation. The pocket 26 is preferably filled with Corning Glass#7570.

The transducer 20 further has a winding window 28 provided in one of thecore members 22 inwardly of the transducing gap plane 32 in a well knownmanner. Transducing windings 33 are arranged preferably around one coremember 22 and they extend through the winding window 28. In thepreferred embodiment the other core member 21 does not carry a windingso that an accurate registration between that core member and areference surface within the core holder can be obtained, as it will bedescribed in more detail below.

A plurality of similar transducers 20 is made preferably during the samemanufacturing process utilizing well known batch fabrication techniques,for example as it is known from the above-mentioned patents. Theabove-described transducers are of the type well known to be utilizedfor example for television signal recording and reproduction. Preferablyall the transducers 20 utilized in the same multichannel head of theinvention are made from the same block of magnetic material and duringthe same batch fabrication process to assure a desired uniformperformance on all the transducing channels.

It is noted that in the attached drawings like elements are designatedby like reference numerals throughout the drawing FIGURES.

FIG. 2 shows a perspective view of a multichannel transducer core holder45 in accordance with the preferred embodiment of the invention. Theholder 45 is made from a block of nonmagnetic material, for example ATD48 made by Ampex Corporation, machineable glass-ceramic, or nonmagneticferrite. Selection of the type of material for holder 45 is made withrespect to the intended application, such as contact or non-contactrecording, while considering wear, when appropriate. The material of thenonmagnetic holder 45 is selected to be easily machineable and to havecompatible physical and mechanical properties with the material of themagnetic cores 21, 22, such as similar coefficients of thermalexpansion.

The transducer holder 45 is preferably manufactured as follows. Arectangular block of nonmagnetic material is provided with an uppersurface 46 and a lower surface 47 parallel with surface 46. Thereafter aplurality of precision parallel grooves 48 is provided in the block 45inwardly of the upper surface 46. The grooves 48 are preferably cut by acommercially available automatic slicing saw (not shown), such as madeby Disco Abrasive Systems, Ltd. In the preferred embodiment one lateralsurface 49a of a first cut groove 48 serves as a common referencesurface for determining the pitch L1 between adjacent grooves, whichcorresponds to the track pitch of the multichannel head. Consequently,the surface 49b of the second cut groove 48 adjacent to the first grooveis spaced at a distance L1 from the common reference surface 49a. Thenext cut groove 48 will have its lateral reference surface 49c spacedfrom the common reference surface 49a at a distance L2=2L1. Thus eachsubsequent lateral reference surface will be spaced from the commonreference surface 49a by a progressively increasing integral multiple ofL1. The resulting track pitch L1 is uniform and can be obtained with aprecision limited only by the precision of the saw, which in thepreferred embodiment is ±40 microinches. Because each subsequently cutgroove is referenced to the same common reference surface, the trackpitch tolerances do not accumulate except as being limited by theperformance of the saw.

The width c of each groove 48 is selected greater than the previouslydescribed width W2 of the transducer 20 of FIGS. 1A and 1B. In thepreferred embodiment for example c=0.025 inch and W2=0.007 inch. Adesired uniform width c and uniform depth d of the grooves 48 isobtained as follows. First the plurality of lateral reference surfaces49a to 49n is cut with a relatively narrow cutting wheel, for examplehaving a width of 0.005 inch. The pitch of each subsequently cut surface49b to 49n is referenced to the first cut surface as previouslydescribed. The reference lateral surfaces 49a to 49n are cut slightlydeeper than a desired depth d of grooves 48 to obtain an undercutportion 53 as shown in FIG. 2. The undercut portion 53 provides a reliefbetween a bottom surface 54 of the grooves 48 and the reference lateralsurfaces 49a to 49n as it will follow from further description.

After the reference surfaces are cut as above described a second cuttingwheel (not shown) is utilized which is wider than the first used wheelbut slightly narrower than the desired width c of the grooves 48. Forexample, in the preferred embodiment the second cutting wheel may beselected 0.022 inch wide. The grooves 48 are then cut wider by thesecond cutting wheel to the desired width c of 0.025 inch in a wellknown manner. It will be understood by those skilled in the art thatduring the process of widening the grooves 48 with the second cuttingwheel, the previously cut reference surfaces 49a to 49n should stayintact to assure proper definition of these reference surfaces.

As it is shown in FIGS. 2 and 3A, the depth d of the grooves 48 isprovided slightly larger than the length s of the core member 21 toobtain better support of the transducer at the transducing gap plane asit will be explained later in more detail.

It is seen from the foregoing description and from FIG. 2 that byproviding the undercuts 53 any undesirable radius between the surfaces49a to 49n and surface 54 is eliminated. As well known in the art, sucha radius between two rectangular surfaces is obtained due to theimperfection of cutting tools. By removing the undesired radius from thegrooves 48 all the transducers 20 inserted in grooves 48 will besupported by the bottom surface 54 at a uniform depth d from the uppersurface 46. The foregoing provision is useful in preventing gap scatterwithin the multichannel head as it will become more apparent fromfurther description.

After the grooves are cut as above described, an individual magnetictransducer 20 is inserted into each parallel groove 48 in accordancewith the preferred embodiment as follows.

FIG. 2 shows an exploded view of a transducer 20 and a locating spring55 to be inserted into the same groove 48 with the transducer. A lateralsurface 19 of the transducer 20 abuts the reference lateral surface 49aof the groove. The leaf spring 55 is inserted adjacent to the otherlateral surface 18 of the transducer, opposite surface 19. Preferably acommercially available leaf spring is used. The leaf spring 55 serves tofirmly hold each transducer 20 in a desired position during alignmentwithin the holder and during mechanical and electrical testing, prior tothe final bonding of the transducers with the holder 45. The leaf springis preferably made of a nonmagnetic flexible material which issufficiently stiff to hold the transducers in place during alignment andassembly. In the preferred embodiment the leaf spring 55 is made ofberylim copper, but it may be made of another suitable metal or plasticmaterial.

Alternatively, as the locating element 55 a wedge may be utilized toforce the transducer 20 against the reference lateral surface. The wedgemay be made of a nonmagnetic material, for example metal or plastic,having mechanical properties compatible with those of the material ofthe holder 45.

As it is seen from FIG. 2, the transducers 20 are inserted into thegrooves 48 with their core members 21 which do not have transducingwindings thereon, while those portions of core members 22 which carrythe transducing windings extend from the grooves. The foregoing featureis useful for obtaining precise abutment of the transducer cores withthe reference surfaces 49a to 49n. It is preferable that the grooves 48have a depth d slightly larger than the length s of the core members 21to obtain a desired support for the transducing gap plane 32 providedbetween the core members 21, 22.

After all the transducers 20 and locating springs 55 and inserted intothe parallel grooves 48, the individual transducers 20 are aligned toobtain a desired precise alignment at the face portions 27 of all thetransducers as well known. Thereafter, each transducer 20 is examined todetermine whether any mechanical damage has occurred during theassembling process, such as chipping, cracking or breaking of the coresor whether the transducing gap has been damaged. The electricalperformance of the transducers 20 is also tested. Those transducerswhich do not meet the specifications are replaced. When all the alignedtransducers 20 satisfy the requirements, a cover piece 70 is placed overthe holder 45 and the entire assembly is bonded together, preferablypotted with epoxy, utilizing well known bonding techniques. It is notedthat the epoxy material is not shown in the drawings for better clarityof representation.

The cover piece 70 is preferably made by machining a rectangular blockof nonmagnetic material, preferably the same material as that of thenonmagnetic holder 45. The cover piece 70 has an upper surface 71 and aparallel lower surface 72. A recess 73 is provided in the cover piece70, preferably by machining inwardly of the lower surface 72. The recess73 extends over the portion of holder 45 comprising the transducers 20.The depth of the recess 73 is selected to slightly exceed the height ofthe portion of transducers 20 extending over the upper surface 46 ofholder 45 which portions carry the transducing windings.

After the transducers 20 and locating springs 55 are inserted in thegrooves 48 and aligned as previously described, the cover 70 is placedover the holder 45 with the upper surface 46 of the holder and lowersurface 72 of the cover abutting.

FIGS. 3A to 3C respectively show a top, side and front elevation view ofa resulting integrally joined multichannel head assembly 58 of theinvention, basically corresponding to the above-described embodiment ofFIG. 2. However, there is a difference in that in FIGS. 3A to 3C,transducers 20 are arranged in the grooves 48 with their face portions27 slightly extending from the holder 45. For example, the face portions27 may extend over the front surface 57 of the holder by 0.003 inch.Thereby a unit pressure between the transducer and recording medium ismaximized. The foregoing serves to minimize head-to-medium separationlosses as it is well known for obtaining optimum high frequency responsein contact recording or reproduction.

Alternatively, the face portion 27 of transducers 20 can be made flushwith the front surface 57 of the holder 45, as it has been shown in FIG.2.

In both instances, that is, whether the transducer faces extend from theholder or are made flush therewith, the integrally joined multichannelstructure may be contoured in a well known manner.

FIGS. 4A and 4B show an alternative embodiment of the modularmultichannel transducer assembly of the present invention. Because ofthe similarities of the multichannel transducer assembly 80 of FIGS. 4Aand 4B to the previously described preferred embodiment of FIGS. 2 to3C, only the differences from the previously described embodiment willbe described to avoid repetition.

In the transducer core holder 81 a plurality of parallel grooves 82 isprovided inwardly of an upper surface 83, in a similar manner aspreviously described. In this alternative embodiment the transducers 20are located in the grooves 82 in a position obtained by rotating by 90degrees with respect to the position of the transducers 20 in the holder45 of FIGS. 2 to 3C. As it is seen from FIGS. 4A and 4B, the transducers20 are supported by the bottom surface 84 of the grooves 48 at theirrear surfaces 50, opposite their face portions 27.

Preferably the depth d1 of the grooves 82 is such that only a portion ofthe transducer core which is free of the transducing windings 33 issupported within the groove by a respective reference lateral surface86a to 86n. To obtain the foregoing, the depth d1 of the grooves 82 isselected to correspond to the distance between the winding window 28 andthe rear surface 50 of the transducer 20, as it is shown in FIG. 4A. Asa result, transducing winding carrying portions of the transducer coremembers 21, 22 extend above the upper surface 83 of holder 81.

A locating means 85 is provided, preferably in the form of a leafspring, which is similar to the previously described locating means 55of FIG. 2. After all the transducers 20 have been inserted into thegrooves 82 as above-described and shown in FIGS. 4A and 4B, with awinding free portion of each lateral surface 90 abutting a referencesurface 86a to 86n, respectively, the leaf spring 85 is inserted in eachgroove to urge the transducer core against that reference surface,similarly, as it has been previously described.

In the presently described embodiment of FIGS. 4A, 4B the individualtransducers 20 are carefully inspected for mechanical and electricaldefects and imperfections and those transducers which do not satisfy therequirements are replaced. Then all the transducers 20 are alignedwithin the holder 81 to obtain a desired precise alignment of thetransducing gaps 23. Thereafter they are firmly attached to the holderfor example by a well known epoxy or glass bonding technique.

When comparing the alternative embodiment of FIGS. 4A, 4B to thepreviously described preferred embodiment of FIGS. 2 to 3C, it has anadvantage that the transducing windings may be placed over both coremembers, rather than just over one core member as in FIGS. 2 to 3C.However, in the embodiment of FIGS. 4A and 4B a relatively largerportion of the transducer face remains unsupported.

An example of utilizing the modular multichannel head of the inventionto obtain recording or reproduction on high density narrow tracks of amagnetic medium is shown in FIG. 5 and will be described below.

FIG. 5 shows schematically a plurality of identical modular multichannelheads of the present invention which are spaced from each-other along amagnetic medium in a well known manner to obtain interlaced recordingtracks provided by the respective channels of each head. For example,all the respective multichannel heads may be of the type shown at 58 inFIGS. 2 to 3C or of the type shown at 80 in FIGS. 4A and 4B.

The multichannel heads 58 shown in FIG. 5 are spaced from each-other ina staggered relationship such a way that the transducing gaps 23 of eachtransducer 20 of any head 58 are offset with respect to the transducinggaps of any other head 58 across the recording medium 92. Eachtransducing gap 23 is aligned with a particular recording track of therecording medium 92 which track is spaced at a predetermined smalldistance from an adjacent track on that medium. In FIG. 5 the medium 92,for example a magnetic tape, moves in a longitudinal directiondesignated by arrow 93 and the transducing gaps 23 of the respectiveheads 58 are offset in a direction substantially perpendicular todirection 93. As the tape passes under the transducing gaps 23 of thuslyspaced transducers 20, which are for example in a recording mode, aplurality of interlaced recorded tracks 94 is obtained as it is wellknown in the art. A plurality of high density narrow tracks may bethereby obtained.

It is noted that for better clarity of representation, in FIG. 5 themultichannel heads 58 are shown as being rotated by 180 degrees, thatis, having their front surfaces 57 and transducing gaps 23 facing theviewer rather than the surface of the magnetic tape 92.

In addition to the advantages of reduced rejection rate as it has beendescribed above in connection with the modular multichannel head of theinvention, it is seen from the foregoing description that the presentinvention has the advantage of utilizing only a single precision cuttransducer core holder or side piece for each multichannel head. Theindividual transducers are referenced against precision surfacesprovided directly in the holder. Thereby a need for precision gauges toobtain accurate channel-to-channel locations in the multichannel head iseliminated.

It is further seen from the disclosure that commercially available batchfabricated individual transducers can be utilized in the respectivetransducing channels of the multichannel head of the invention. Themanufacturing process is thereby considerably simplified when comparingto known processes of making prior art multichannel heads.

What is claimed:
 1. A method of making a modular multichannel magnetichead assembly, comprising the steps of:providing a plurality ofindividual magnetic transducers, each having a magnetic core with twoconfronting poles defining a transducing gap therebetween and eachtransducer core having two opposite lateral surfaces defining a width ofsaid transducer; making a nonmagnetic holder with a plurality ofparallel grooves therein and forming a reference lateral surface withineach said groove, said grooves having a width greater than the width ofsaid transducers, the reference surfaces of each groove being spaced apredetermined distance from each other; inserting one said magnetictransducer in each said groove with a first said lateral surface of saidcore abutting said reference lateral surface of said groove; arranging alocating means in each said groove adjacent a second lateral surface ofsaid transducer for urging said first lateral surface against saidreference lateral surface; adjusting said individual magnetictransducers within said grooves to have their respective transducinggaps aligned; and integrally joining said transducers with said holder.2. The method of claim 1 wherein the step of arranging said locatingmeans in each said groove comprises inserting a leaf spring in each saidgroove adjacent said second lateral surface.
 3. The method of claim 1wherein the step of integrally joining said transducers with said holdercomprises a bonding step.
 4. The method of claim 1 further comprisingthe step of inspecting said individual transducers for mechanical andelectrical damages thereof and replacing damaged transducers prior tothe step of integrally joining the transducers with the holder.
 5. Themethod of claim 1 wherein the step of providing a plurality of parallelgrooves comprises providing a first groove in said holder having areference lateral surface and providing a second and subsequent grooveshaving respective parallel reference surfaces spaced at predetermineddistances from said reference surface of the first groove.
 6. The methodof claim 5 wherein the step of providing said plurality of parallelgrooves further comprises cutting each said groove with a narrow bladeto obtain said reference lateral surfaces and thereafter enlarging thewidth of said grooves by cutting with a wider blade to obtain a desiredwidth of said grooves.
 7. The method of claim 6 further comprising thestep of cutting said grooves with said narrow blade at a depth greaterthan provided by said wider blade.
 8. The method of claim 1 wherein thestep of providing a plurality of magnetic transducers comprisesproviding each transducer with a first and a second confronting coremember abutting at a transducing gap plane and having a transducing gapdefining face portion, forming a transducing winding window in saidfirst core member inwardly of said transducing gap plane, winding atransducing winding around said first core member and through saidwinding window, and wherein the step of inserting a transducer in eachsaid groove comprises having said first lateral surface of said secondcore member and of a portion of said first core member which is free oftransducing winding abutting the reference lateral surface within saidgroove, while having a transducing winding carrying portion of the firstcore member extending from said groove.
 9. The method of claim 8 whereinthe step of adjusting said transducers within said grooves comprisesaligning said transducing gap defining face portions flush with a frontsurface of said holder.
 10. The method of claim 8 wherein the step ofadjusting said transducers within said grooves comprises aligning saidtransducers to have their transducing gap defining face portionsextending from an upper surface of said holder.
 11. The method of claim8 where said portions of said first core members extend above an uppersurface of said holder, further comprising the steps of providing acover piece of a nonmagnetic material, providing a lower surface on saidcover piece confronting said upper surface of said holder, providing arecess in said cover piece for accommodating said extending portions ofsaid first core members and assembling said cover piece with said coreholder with said confronting surfaces abutting prior to said integrallyjoining step.
 12. The method of claim 1 wherein the step of providing aplurality of magnetic transducers comprises providing each transducerwith two confronting core members abutting at a transducing gap planeand having a transducing gap defining face portion, forming atransducing winding window in at least one core member inwardly of saidtransducing gap plane and winding a transducing winding around at leastone core member and through said winding window; andwherein saidinserting step comprises supporting a rear surface of each saidtransducer, opposite said face portion by a bottom surface of saidgroove, and supporting a winding free portion of said first lateralsurface of both core members by said reference lateral surface withineach groove while having a portion of the transducer including thetransducing winding and the transducing gap extending from said groove.13. The method of claim 1 further comprising the step of arranging atleast two identical multichannel head assemblies with their respectivetransducing gaps offset with respect to each-other in a directionsubstantially perpendicular to a direction of movement of said recordingmedium.
 14. A method of making a modular multichannel head assemblycomprising the steps of:providing a plurality of individual magnetictransducers, each having a first and a second confronting magnetic coremember abutting at a transducing gap plane and having a transducing gapdefining face portion, each transducer having two opposite lateralsurfaces defining a width of said transducer; forming a transducingwinding window in said first core member inwardly of said transducingplane and winding a transducing winding around said first core memberand through said winding window; making a nonmagnetic holder; cutting aplurality of parallel grooves in said holder inwardly of an uppersurface thereof at a selected depth, while forming a reference lateralsurface within each groove spaced at a predetermined distance from acommon reference surface, said grooves having a width greater than saidtransducer width; inserting one said magnetic transducer in each saidgroove with a first lateral surface of said second core member and aportion of said first core member which is free of transducing windingabutting said reference lateral surface of said groove, while having atransducing winding carrying portion of the first core member extendingfrom said groove; arranging a locating means in each said grooveadjacent a second lateral surface of said transducer for urging saidfirst lateral surface against said reference lateral surface; adjustingsaid individual magnetic transducers within said grooves to have theirrespective transducing gaps aligned; and integrally joining saidtransducers with said holder.
 15. A method of making a modularmultichannel head assembly comprising the steps of:providing a pluralityof individual magnetic transducers, each having a first and a secondconfronting magnetic core member abutting at a transducing gap plane andhaving a transducing gap defining face portion, each transducer havingtwo opposite lateral surfaces defining a width of said transducer;forming a transducing winding window in at least one core memberinwardly of said transducing plane and winding a transducing windingaround at least one core member and through said winding window; makinga nonmagnetic holder; cutting a plurality of parallel grooves in saidholder inwardly of an upper surface while forming a reference lateralsurface within each groove spaced at a predetermined distance from acommon reference surface, and forming a bottom surface in each groove ata selected depth from said upper surface, said grooves having widthgreater than said transducer width; inserting one said magnetictransducer in each groove in such a way that a rear surface of saidtransducer, opposite its face portion is supported by the bottom surfaceof said groove and that a portion of said first lateral surface of bothcore members which portion is free of transducing winding is supportedby said reference lateral surface while a portion of the transducerincluding the transducing winding and transducing gap extends from thegroove; arranging a locating means in each said groove adjacent a secondlateral surface of said transducer for urging said first lateral surfaceagainst said reference lateral surface; adjusting said individualmagnetic transducers within said grooves to have their respectivetransducing gaps aligned; and integrally joining said transducers withsaid holder.